Water pipes

A method of magnetorheological processing of surfaces of optical parts with a small tool. Machine for finishing, aspherization and polishing of optical parts "technological processing

The purpose of polishing is to give the surface used the required transparency and values of N, DN, P. The process of polishing glass with aqueous suspensions of polishing powders is more complex than grinding physical and chemical nature. When polishing, it is required to achieve a surface roughness of not more than 3-5 hundredths of a micron. In accordance with GOST 2789-73.

The outer relief layer formed by grinding is completely removed by polishing, while the cracked one remains partially, but the cracks on the surface are polished by particles of hydrolyzed glass and do not interfere with the passage of light through it.

Externally, the picture of the polishing process is as follows. Grains of polishing powder, consisting mainly of oxides of cerium or iron, have a size of 0.2 - 2 microns, they are suspended in water and are located between the lapping surfaces of the polishing pad and glass.

Compared to grinding powders, grains of polishing powders have lower hardness and less pronounced abrasive properties of self-sharpening when splitting. The splitting and blunting of the grains of polishing powders, in most cases having a size of 0.2 - 1.0 microns, can be judged only by secondary indirect signs.

The polisher has a resin working layer. The areas of surface irregularities of the polished glass surface and the resin surface of the polishing pad are much larger than the grain sizes of the polishing powder. But on glass, the irregularities of the ground surface have a microgeometric characteristic, and on resin, they have a macrogeometric characteristic. The working surface of a viscous resin polishing pad, being plastically deformed, is smoothed out along the microroughness of the polished surface.

The water, in which the grains are suspended, at the first moments of the suspension supply, exerts a hydrostatic counterpressure to the outside, and then spreads and the grains are fixed, being adsorbed in the outer layer of the resin. Part of the grains that have not yet fixed in the resin rolls, or, having fixed for a moment, continues to move in the direction of the relative velocity vector .

The grains cut off the tops of the relief layer, which immediately become smooth and polished. In the future, the dimensions of the polished areas increase, the height of the irregularities decreases to those characteristic of the 13-14th roughness classes.

Rolling grains, fixing (adsorbing) in the resin, and at the same time in the remnants of cavities, pores and grooves, on the polished elementary glass areas, as it were, stick them together with the surface of the polishing pad and subsequently, with relative movement, tear off pieces of the colloidal film formed on the glass surface under chemical influence water.

The residual unevenness of the polished surface is less than 0.03 µm, i.e. less than the wavelength of visible radiation, since the size of the part of the grain that penetrates the glass does not exceed 0.3 microns.

The plastic properties of the resin holding the grains and the colloidal film ensure that the work of the grains of the polishing powder is not accompanied by the appearance of scratches with torn edges and cracking of the glass in width and depth. Due to the plastic properties of the colloidal film of silicic acid, the grooves formed from the removal of the "chips" are tightened. The cracks remaining from grinding are filled with colloidal products of glass hydrolysis.

For technological and design calculations, it is assumed that the kinetic energy consumed in the relative motion of the elements of the kinematic pair of glass-tool goes to overcome the resistance of glass to cutting by its grains of polishing powder. Elementary forces on each grain and integral cutting gain of polishing are static.

The integral sum of elementary forces forms the force of interaction between the glass and the tool, which is the payload of the machine during polishing. When polishing, a small but quite noticeable layer of allowance is removed, just as it was done with respect to grinding.

During polishing, the chemical process is manifested in the fact that water, acting on the glass, forms a colloidal film. The film thickness increases rapidly depending on the chemical resistance of the glass of the given grade, reaching its maximum thickness in approximately one minute. Previously, it was believed that the polishing process can proceed when the grains interact only with a colloidal film, but now the processing modes have become so intense that the film does not have time to form and the grains of the polishing powder act on glass that does not have a surface film. It is proved that in this case, too, a polished surface of the 13th and 14th roughness classes is formed.

Thus, the mechanical action of the grains is of predominant importance and its strengthening increases the efficiency of glass polishing. When polishing with the help of mechanical influences, it is possible to control the process of surface formation with given values of N, and P.

On a polished surface, in addition to irregularities, the values of which are specified by the 13th and 14th classes according to GOST 2789 - 73, there can always be defects. Roughness defects remain from the ground structure or appear as scratches on the surface of the machined part.

Scratches during the polishing process are formed when particles harder and larger than the grains of the polishing powder get under the tool. The sizes of defects in the purity of polished surfaces of optical parts are normalized and indicated by the corresponding values in GOST 11141 - 76.

Polishing is performed on the same machines as grinding, but at a lower rotational speed of the working bodies. Grinding takes minutes and polishing takes hours, i.e., the time is approximately 20 times longer than the grinding time.

Fig.13.1 Scheme of work of fixed abrasive grain

Bonding connection. The most common way to connect optical parts to each other is to glue them together. The choice of glue brand, gluing technology and additional heat treatment is determined by the size and material of the parts to be glued, the quality of the mating surfaces (surface stress error and surface cleanliness), technical requirements for the connection, and adhesive properties.

Usually, the technological process of gluing optical parts includes the following main operations: preparation of parts for gluing, preparation of glue, application of glue, mutual alignment of parts to be glued and fixation of the found position, removal of glue from the side surfaces, exposure of the glued joint under specified conditions, control.

1. Preparation of parts consists of two successive operations - assembly of parts and cleaning of surfaces to be glued with organic solvents. The complete set of lenses reduces the total error of the thicknesses of the glued lenses and thus ensures the achievement of the specified values of focal lengths and image quality. When assembling lenses, the following conditions must be met:

a) the algebraic sum of the deviations of the thicknesses of the individual lenses of a two-lens set must be minimal and satisfy the requirements of the drawing. For three-lens sets, the thickness deviation of one of the lenses must be equal in absolute value and opposite in sign to the sum of the thickness deviations of the other two.

To ensure the conditions for the assembly of two- or three-lens sets glued in this way with other elements of the optical system, the components must have certain (in sign) deviations from the nominal value;

b) the accuracy of the mating of the surfaces to be glued must be.

The surfaces of the lenses to be joined are washed, cleaned, placed one on top of the other and set in sets on a plane strictly aligned with the horizon.

The complete set of prisms at the corners reduces the errors in the angles of deflection of the rays, other geometric parameters, improves the image quality by reducing chromatism.

2. Glue preparation depends on the selected brand of glue. Test tubes with balm are heated in a water bath to a temperature of 130-135 °C. Synthetic adhesives consisting of several components are thoroughly mixed in a test tube using a mechanical mixer.

3. Glue is applied using a glass stick - a dropper on the upper concave surface of the lower lens. Then the upper lens is superimposed and the wooden handle with suede or cork washer is smoothly rubbed in a circular motion to the lower one. In this case, air bubbles are squeezed out along with excess glue. The optimal thickness of the adhesive layer is 0.005-0.01 mm. Excess glue is removed with a cloth moistened with organic solvents.

4. Adjustment and fixation of the found position of the parts to align the optical axis of the glued lens set with the geometric axis of the lower - side is performed using centering autocollimation microscopes. For gluing plates, wedges and prisms, special devices are used, including collimators, spotting scopes, microscopes and adjustment devices.

5. Removal of glue from the side surfaces of the glued parts is performed mechanically. Sometimes they are additionally wiped with a cotton swab dipped in a solvent.

6. Exposure of glued parts under specified conditions is carried out in thermostats or in a room under electric lamp heaters.

7. The control of glued parts is carried out by sticking and scratches, and by the accuracy of surfaces and geometric parameters.

Bake connection. They are used to ensure the high resistance of parts such as cuvettes to chemical, thermal, mechanical influences. Before sintering, the surfaces are cleaned and wiped with organic solvents.

The paste is then applied to the surfaces to be sintered using a glass rod. The mutual orientation of the found position is carried out on special tables or with the help of strubia.

The temperature of the furnace, the time and mode of sintering and cooling of the furnace depend on the brand of glass, the dimensions of the parts and the composition of the paste.

Optical connection. In some cases, in order to more accurately relative orientation of the parts to be joined, optical contact is used. To do this, carefully cleaned and washed surfaces are compressed to remove air between them.

The criterion for the quality of the connection is the absence of light shades and spots in the contact plane, observed under side illumination.

To protect against spontaneous removal of parts from the contact, the joints are varnished or sealed. Preliminary deposition of a thin silica film on the contacting surfaces, followed by heating at 250 °C, makes the connection inseparable.

Such a connection is called “deep optical contact”, which significantly expands the scope of optical contact, replacing sintering and welding.

Welding connection. Welding of quartz parts is carried out in the flame of an oxygen-hydrogen burner at a temperature of 2000 °C. The high temperature of local heating causes crystallization of the surface layer, which leads to deformation of the parts.

Solder connection. The operation is performed by laser radiation focused into the plane of the seam containing light-absorbing solder. For this, special technological laser installations are used with the ability to accurately move the beam along the joint.

Ministry of Education of the Republic of Belarus

educational institution

"BELARUSIAN STATE UNIVERSITY

INFORMATION SCIENCE AND RADIO ELECTRONICS»

ABSTRACT

On the topic of:

"TECHNOLOGICAL PROCESS OF PROCESSING

OPTICAL PARTS (general basics)"

MINSK, 2008

Basic technological operations

The technological process of manufacturing optical parts consists in processing their working and mounting surfaces. Blanks (lump glass, tiles, pressing, etc.) are given the required dimensions, and surfaces are given a structure in accordance with their purpose.

When drawing up the most appropriate technological process, the type of raw material, the number of parts in a batch, the available technical means (equipment, tools, etc.) and the required manufacturing accuracy should be taken into account. The processing of many optical parts can be divided into several main stages, each of which has a specific purpose.

blank. Procurement operations are the removal of excess material, giving the workpiece an accurate shape, maintaining the desired dimensions, providing the desired surface structure (haze) for subsequent fine grinding.

Operations for obtaining a semi-finished product can be very diverse. These are glass cutting, sawing, milling, drilling, rounding, peeling, medium grinding, chamfering, etc. Processing is carried out with abrasives in a free or bound state (circles, milling cutters, diamond ceramic-metal tools). In many operations (sphere grinding, centering, milling, faceting), tools made of synthetic diamonds on a metal-ceramic bond are widely used.

Auxiliary operations (sticker, gluing, blocking, etc.) are used to attach parts to fixtures and group them for joint further processing or to remove all kinds of contaminants (washing, wiping).

fine grinding. This is the preparation of the surface of an optical part for polishing, i.e., the removal of allowances on the workpiece and bringing the dimensions of the sides to the specified ones due to successive processing with abrasives of various sizes (the so-called transitions). As a result of fine grinding, a matte surface texture with a very fine structure is obtained.

The abrasive grains, when rolling between the glass and the grinder, damage the glass with their cutting edges. Due to the shock-vibration action of the abrasive grains, a damaged surface layer (protrusions and conchoidal fractures) is formed on the glass, and under it an internal cracked layer. The depth of the fractured layer is several times (4 or more) greater than the depth of the knockouts of the surface layer (studies by N. N. Kachalov, K. G. Kumanin and other scientists).

If there is excess water during grinding, the grains are washed off, the pressure on each remaining grain increases, they are crushed or jammed. In this case, scratches and gouges are inevitable. Excess abrasive, preventing the grains from rolling freely, causes scratches and reduces productivity. Grinding is most productive when the abrasive grains are distributed in one layer.

The spindle speed affects the frequency of grains rolling and their shock-vibration action. An excessive increase in speed causes, under the influence of centrifugal force, the dropping of grains that have not yet been used.

The amount of grinding is proportional to the amount of pressure. Practically limiting is the pressure at which the grain is crushed (crushing force). Its value depends on the strength of the abrasive used.

It has been established that water causes chemical processes on the glass surface, as a result of which wedging forces are created that contribute to the separation of glass particles from the treated surface.

Polishing. This is the operation of removing the remaining irregularities on the surface of the optical part after fine grinding to obtain the required class of roughness and cleanliness, as well as to obtain the specified accuracy in terms of flatness or curvature of the treated surface. The process is based on the combined action of a number of factors: mechanical, chemical and physico-chemical

The use of various wetting liquids, as experiments have shown, can speed up or slow down the polishing process. It has been proven that siliceous glass compounds under the influence of water form the thinnest (from 0.0015 to 0.007 microns) film, which stops water from accessing deeper layers of glass and its chemical effect on them. Due to mechanical forces, this film is torn off, exposing a fresh layer of glass, which is again exposed to water. As a result, a new layer of film is formed, which immediately breaks off, etc. The film itself is capable of retaining polishing material particles on its surface by cohesive forces.

As a polishing tool, faceplates, mushrooms and cups are used, on which a layer of resin or fibrous materials is applied.

For double-sided polishing of stained glass, mirror glass, construction glass, and decoration of high-quality glassware, it is of great importance to improve the methods of chemical (acid) treatment of glass surfaces by etching. This method can be used instead of mechanical polishing of the glass surface, sometimes in combination with mechanical methods.

Centering. This is the operation of processing a part in diameter symmetrically to its optical axis, in which both the optical and geometric axes of the lens are combined. The need to perform the operation is caused by the following circumstances. In the process of manufacturing blanks, for example, when rounding columns (Fig. 1, a), peeling, grinding and polishing due to uneven removal of the glass layer, the lenses can have a wedge-shaped, which is characterized by uneven thickness of parts along the edge (Fig. 1, b). In such a detail, when applying a sphere, the centers of the spherical surfaces, and, consequently, the optical axis are shifted relative to the geometric axis of the lens.

Fig.1. Scheme of formation of decentering:

a - skew of the axis of the column of blanks; b - displacement of the center of the spherical surface

Rice. 2. Decentering in the lens:

a - the optical axis is parallel to the geometric axis; b - optical axis at an angle of the geometric axis

Rice. 3 Schematic representation

Fig.4. Automatic lens mounting by compression between cartridges:

1-lens; 2-cartridges

The optical axis of the lens before the centering operation can be parallel to its geometric axis (Fig. 2, a) or go at some angle to it (Fig. 2, b). In such a lens, its edges are located at different distances from the optical axis and have different thicknesses. Such a lens cannot be placed in the frame of the device, since the image will be poor (the optical axis of the lens does not coincide with the geometric axis of the frame). The edges of a centered lens have the same thickness, and the optical and geometric axes are aligned within the decentering tolerance (Fig. 3b).

The installation of the lens on the cartridge before centering is carried out optically or mechanically.

Optical method - installation by "glare" on the eye or under the optical tube. The lens is fixed with a centering resin on a rotating cartridge in a position in which the immobility of the image of the lamp filament or the image of the "glare" in the optical tube is ensured.

The mechanical method (self-centering) consists in the fact that the lens is installed automatically by compression between two cartridges located strictly on the same axis (Fig. 4).

With both methods, the correct installation is guaranteed by good preparation and trimming of the mounting edge of the cartridges and the absence of runout of the centered part during rotation.

Gluing. The task of gluing is to obtain a rigidly fastened and centered system.

In some cases (especially for flat parts), gluing is replaced by optical contact (molecular adhesion of two polished surfaces).

Auxiliary technological operations

The most important auxiliary operation is blocking - the connection of parts or blanks with a device (sticker, mechanically, by optical contact, vacuum fastening, landing in separators, etc.) for their joint further processing. The combination of a fixture and parts or blanks fixed to it is called a block. The quality of the product and the efficiency of the technological process depend to a large extent on the correct choice of the method of blocking, depending on the size and shape of the parts, the given accuracy.

Blocking should provide:

1) fixing the maximum number of blanks;

2) ease of processing in this operation (for example: grinding, polishing);

3) convenience to make the necessary measurements in the process of work;

4) reliability of fastening at the most intensive mode of operation;

5) the absence of mechanical damage and deformation of blanks or parts;

6) the correct and symmetrical arrangement of the processed surfaces relative to the fixture and the processing tool;

7) ease and speed of locking and unlocking.

In optical production, several methods of blocking are used. However, the most common so far is the method of elastic fastening.

Elastic mount. It is used in small-scale and mass production for medium-precision parts. This operation includes the following transitions:

1. Sticker on one of the processed sides of the resin cushion part manually or on a special semi-automatic machine.

Ministry of Education of the Republic of Belarus

educational institution

"BELARUSIAN STATE UNIVERSITY

INFORMATION SCIENCE AND RADIO ELECTRONICS»

ABSTRACT

On the topic of:

"TECHNOLOGICAL PROCESS OF PROCESSING

OPTICAL PARTS (general basics)"

MINSK, 2008

Basic technological operations

Auxiliary operations (sticker, gluing, blocking, etc.) are used to attach parts to fixtures and group them for joint further processing or to remove all kinds of contaminants (washing, wiping).

As a polishing tool, faceplates, mushrooms and cups are used, on which a layer of resin or fibrous materials is applied.

Fig.1. Scheme of formation of decentering:

a - skew of the axis of the column of blanks; b - displacement of the center of the spherical surface

Rice. 2. Decentering in the lens:

a - the optical axis is parallel to the geometric axis; b - optical axis at an angle of the geometric axis

Rice. 3 Schematic representation

Fig.4. Automatic lens mounting by compression between cartridges:

1-lens; 2-cartridges

The installation of the lens on the cartridge before centering is carried out optically or mechanically.

The mechanical method (self-centering) consists in the fact that the lens is installed automatically by compression between two cartridges located strictly on the same axis (Fig. 4).

With both methods, the correct installation is guaranteed by good preparation and trimming of the mounting edge of the cartridges and the absence of runout of the centered part during rotation.

Gluing. The task of gluing is to obtain a rigidly fastened and centered system.

In some cases (especially for flat parts), gluing is replaced by optical contact (molecular adhesion of two polished surfaces).

Auxiliary technological operations

Blocking should provide:

1) fixing the maximum number of blanks;

2) ease of processing in this operation (for example: grinding, polishing);

3) convenience to make the necessary measurements in the process of work;

4) reliability of fastening at the most intensive mode of operation;

5) the absence of mechanical damage and deformation of blanks or parts;

6) the correct and symmetrical arrangement of the processed surfaces relative to the fixture and the processing tool;

7) ease and speed of locking and unlocking.

In optical production, several methods of blocking are used. However, the most common so far is the method of elastic fastening.

Elastic mount. It is used in small-scale and mass production for medium-precision parts. This operation includes the following transitions:

1. Sticker on one of the processed sides of the resin cushion part manually or on a special semi-automatic machine.

2. Cleaning the second treated lens surface

3. Lapping lenses to a carefully cleaned surface of the lapping device (mushroom, cup, faceplate).

4. Gluing parts to the adhesive device.

5. Block cooling.

The thickness of the resin layer after cooling should be 0.1-0.2d (d is the lens diameter), but not less than 1 mm (for small diameter lenses). So, for example, for a lens with a diameter of 30 mm, the height of the resin cushion is 3-6 mm. The diameter of the resin cushion is equal to the diameter of the part and is made with a slight taper for ease of blocking (Fig. 5). Unlocking is done in the refrigerator, and sometimes just with a wooden mallet.

Shading is used for lenses of small diameter and small radius of curvature. Lapped and respectively located on the surface of the lapping device, the lenses are dripped with molten resin from above. The resin fills the cup, warms up the lenses and sticks to them. While the resin has not hardened, a heated adhesive device, such as a mushroom, is introduced into it. After sufficiently immersing in resin and leveling so that the axes of the fixtures coincide, the block is cooled. After stripping, the surface of the block is washed with solvent and water. Unlocking is done by heating the unit.

Rigid mount. It is used in mass and large-scale production of parts with surface accuracy tolerances of 0.5 rings or more, for thicknesses of 0.05 mm or more.

To process the first side, the lenses (pressings) are rigidly glued directly onto the device in special sockets or areas (Fig. 6, a).

Rice. 5. Kind of resin pillows

The device is heated to a temperature of about 100 ° C. At the same time, the parts are slightly heated. A thin layer of resin or a tarred cloth pad is applied to the mounting surface of the device (when processing the second side). After applying the lenses with a stick, the resin from under the part survives as much as possible. After processing the first side (roughening or milling, medium and fine grinding, polishing), the entire surface of the part is varnished and treated in the same sequence on the second side.

Semi-rigid mount. Used for thin lenses with a large radius of curvature of the treated surface. The lens is glued with a tarred cloth gasket onto a metal washer, which, in turn, is glued to the fixture (Fig. 6, b). In spectacle production, a sticker of heated blanks is used directly on the resin layer. To ensure the accuracy of such fastening, a special device forms reverse-shaped seats on the resin layer. They determine the place of the lenses during blocking (Fig. 6c).

Mechanical fastening. It is most often used in harvesting operations, for example, for fixing prisms.

Parts are placed close to each other in metal fixtures with appropriate cutouts. The outer parts are held by screw or spring clamps. An elastic gasket (rubber, cardboard) is placed under the extreme parts.

Rice. 6. Sticker scheme (hard and semi-hard methods):

a - hard method; b - semi-rigid method; c - sticker on resin ledges

(1 - lens; 2 - tarred cloth gasket; 3 - spherical plate;

4 - resin; 5 - sticker fixture);

Gypsum. The method is most often used for fastening prisms with angle tolerances of 3 "and above and large pieces of glass. Gypsum casting consists of pouring an aqueous solution of gypsum with cement into a fixture in the form of a pot, body, etc. (Fig. 7) directly onto the parts lapped to the faceplate.The bottom of the pot is attached to the ring by screws or other means.Often limited to wrapping the lapping faceplate with a rubber rim.After the plaster hardens and the bottom is fixed in it, set directly into the plaster, the rim is removed.The gaps between

Rice. 7. Plastering scheme:

1 - prism; 2 - lapping faceplate; 3 - plate; 4 - bottom; 5 - the ring of the body with prisms after hardening of the gypsum is cleaned with a wire brush to a depth of 2-3 mm and washed.

To ensure the stripping of the block, the space between the prisms before pouring is covered with finely sifted dry sawdust, and the metal rim is placed on 3-4 plates 2-3 mm thick. To protect against moisture and shedding of gypsum, the cleaned space is covered with molten paraffin.

Unblocking is done by splitting the gypsum with a wooden hammer or on a special plaster press. The use of a press reduces the laboriousness of the unlocking process and ensures higher quality, since almost all prisms are completely free of plaster.

Optical contact method. When processing parts with precise surfaces (up to 0.05 rings), angular dimensions 1-2”, parallelism 1-10” (precision plates, mirrors, wedges, prisms), optical contact is used. At the same time, the 0.5-2 rings of the surface of the parts polished “with color” are thoroughly cleaned and degreased (alcohol, ether, squirrel brush, cambric napkins) and smoothly lowered and pressed against the also carefully prepared polished surface of the contact device. Pressure is applied until the interference pattern disappears. The gap between the parts is covered with varnish, or a solution of shellac in rectified.

Contact devices can be of different shapes and sizes (Fig. 8) depending on the shape and size

Rice. 8. Contact devices for plates and prisms: a - contact plate with plane-parallel plates (1 - plates; 2 - contact plate); b - fixture for prisms and wedges (1 - prisms; 2 - contact fixture) of workpieces.

Their surface should be polished with an accuracy of 0.1-0.5 rings. If parallelism is necessary, it can be maintained up to 1-2”. The accuracy of the angles is also strictly maintained, since the quality of the product depends on the accuracy of the angular dimensions, parallelism and quality of the surface of the contact devices.

When removing from contact, heating or cooling is used. Thin parts (0.1-0.5 mm) can be carefully removed with a razor blade or a drop of ether poured onto the surface of the part.

Fastening in separators. Separators or separating devices are used in the workpiece and in final operations for fine-tuning the surface and angular dimensions. The separator is a cage with cutouts into which the workpieces are placed. The processing of such parts, for example, in a workpiece, can be carried out simultaneously from two sides (Fig. 9, a). For fine finishing, thick glass plates with cutouts of different diameters are used, into which various details are laid (Fig. 9, b). The cutouts prevent the part from falling out of the pad.

Rice. 9. Separator: a - two-sided grinding scheme (1 - separator; 2 - plates; 3 - grinders); b-glass separator for mechanized finishing of flat parts

The separator itself constantly corrects the surface of the polishing pad during operation, thereby maintaining it in good condition, i.e. it is also a forming disc.

If on a part (plate, wedge) it is required to increase or decrease the angle of the wedge, then a weight is glued to its edge with soft wax, due to which the desired area is actuated more strongly.

The ratio of the area of the holes and the whole part of the separator is determined by calculation.

Making a set of grinders

Grinding a convex surface when moving from coarser to finer abrasives always starts from the edge. This ensures that the desired thickness of the lens is maintained in the center and uniform grinding of the entire surface from the edges to the center. The radii of curvature of the grinding tool are changed by trimming when moving from larger abrasives to smaller ones.

Rice. Fig. 10. Schematic representations of the change in the radius of curvature of the surface of the cup tool (a) and the mushroom (b):

R 1 - radius of curvature of the peeling tool; R 2 - radius of curvature of the tool for medium grinding; R 3 - radius of curvature of the tool for fine grinding

The radii of curvature of the cups gradually decrease (Fig. 10a), while the radii of the fungi, on the contrary, increase (Fig. 10b).

When grinding a tool, its surface is given the desired radius of curvature or exact flatness. At the same time, the surface is polished until the traces of the cutter or scraper are removed.

The sequence of operation is as follows.

1. The surface of the tool for the last stage of grinding is adjusted by trimming according to a template of a given radius, and then a block of defective parts is blocked on it.

2. On the same tool, the block is ground and polished. An interference pattern (“color”) is visible.

3. If the “color” does not meet the requirements that apply to this set of grinders, then the grinder is re-cut, re-grinded, polished and the “color” is reviewed.

Rice. 11. Lapping scheme:

a - surfaces of small curvature; b - surfaces of large curvature (D bl - block diameter)

4. Upon reaching the required “color”, the tool is ground until the traces of the cutter or scraper are removed, and the block is once again finally checked against the trial glass.

5. When the last grinder is prepared, for example, for grinding with M10 micropowder, the grinder preceding the last one is adjusted (already after lapping), for example, for grinding with M20 micropowder. To do this, a test block is ground on it and its lapping is adjusted to the tool for the last grinding. Blocks with small curvature (with large radii of curvature) should be rubbed in at least ¼ of their diameter, and blocks of large curvature by 1/6-1/7 of their diameter (Fig. 11). There are still names in production: “weak radii” (large radii of curvature), “strong radii”, or “steep spheres” (small radii of curvature). These names should not be used.

6. Under the straightened grinder, the previous one is adjusted, etc. until the entire set is adjusted.

7. Each grinder from the set is ground with the abrasive of the size for which it is intended.

8. For normal block polishing, i.e. for more intensive polishing of the edge of the block, the “color” of the grinding should give a “pit” with a margin of several rings (2-3) against that specified in the drawing.

For example, the finished part should have a “color” N = 3 after grinding, the tool for grinding with the last micropowder, for example, M10 should give a “pit” of 5-6 rings under the test glass on the block.

9. Faceplates should be slightly convex, i.e. give a small “pit” of about 2-3 microns on the part.

The control of the correctness of the surface shape is carried out with a test glass, a glass ruler or an orthotest device. The device is installed with three support pins on the faceplate. The movable tip, located in the center and connected to the arrow, will indicate the amount of deflection. The deviation of the arrow to the right will indicate the presence of a “hillock”, to the left - a “pit”. The central position of the arrow on the scale of the dial (zero position) means a good plane. The scale gives readings in micrometers (µm).

Production of polishing pads

Resin pad. An instrument corresponding in shape and size (mushroom, cup, faceplate) is heated and molten resin is poured onto it, not to a very liquid state. Sometimes, resin crushed in the form of small lumps is poured onto a heated tool and leveled with a special spatula, while maintaining the desired thickness and uniformity of the layer over the entire surface of the tool.

After some thickening of the resin substrate, its final molding is carried out with a moistened block or a special molding device of the desired radius of curvature. A small indentation is made in the center of the layer, and the edges of the polishing pad are cut with a knife.

Cloth polisher. The pad for the polishing pad is cut according to the pattern. Very fleecy materials burn slightly. For a smoother sticker, if you have thick material, soak it in water and wring it out well.

After warming up the corresponding tool (mushroom, cup or faceplate), cover its surface with crushed resin, put a substrate (cloth, felt) on top and crimp it in a special shape (crimp) or in a block manually or on a press.

Both resin and cloth polishing pads, while the substrate is not firmly adhered, are moistened with a polishing suspension and polished with a block until it is given the desired shape.

Polishing precision optical surfaces (resin polishing)

As noted above, the quality of polishing to a large extent depends on the correctness of all previous operations (sticking, blocking, grinding, etc.), the quality of the main processing and auxiliary materials used (abrasive, resin, etc.), the constancy of temperature and room humidity (+20° ± 1°), etc.

In production, a number of operations and tool preparation are carried out by special workers. So, for example, gluing, blocking, making polishing pads, grinding tools are often separated into independent operations.

Nevertheless, checking by the worker himself of the quality of the tool, stickers and blocking must be carried out without fail. Wrongly done work must be redone.

Lenses (elastic method) must not protrude beyond the edges of the adhesive device. Lenses should not be set too high or, conversely, too flooded.

Resin between lenses must be removed.

Lenses without chamfers, with sharp edges, chamfered with coarse abrasives, can give

Rice. 12. Scheme of trimming the extreme zone of the polishing pad: a - during rotation of the polishing pad; b - with a fixed polishing pad

In the polishing process, a number of points are taken into account to adjust the process.

If the part has more edges (“bump”), then the polishing pad is trimmed with a knife edge that part that triggers the edge of the part, i.e., the extreme zone of the polishing pad (Fig. 12). On the contrary, if the part has a more worked out middle (“pit”), the middle zone of the polishing pad is trimmed (Fig. 13).

If the block (or part) is at the bottom, then with mutual grinding, it will always work out more edges, and if it is on top, the middle. Therefore, sometimes they change the relative position of the block and the tool.

In table. 1 gives some practical guidance on how to control the course of the polishing process on resin by changing the nature of the trimming, kinematics and modes.

When working with drying, it is more difficult to maintain the “color”, i.e., the given curvature of the surface, but polishing occurs faster. You should always try to conduct the process (in fine work) so that the remains of the matte surface come off simultaneously with the achievement of the specified accuracy.

When working on felt and where high surface accuracy is not required, intensive modes, pressure, automatic suspension supply are of particular importance, which contribute to the fastest removal of matte surface residues, i.e. increase in labor productivity.

Table 1

Literature

1. Reference technologist-optics, edited by M.A. Okatova, Polytechnic St. Petersburg, 2004. - 679 p.

3. Applied optics, edited by Dubovik A.S. Mashinostroenie, 2002. - 470 p.

4. Pogarev G.V. Adjustment of optical devices Mashinostroenie, 1982. - 320 p.

5. Reference technologist-machine builder in 2 parts. Edited by A.M. Dalsky, A.G. Kosilova, R.K. Meshcheryakova. Engineering 2001

Ministry of Education of the Republic of Belarus

educational institution

"BELARUSIAN STATE UNIVERSITY

INFORMATION SCIENCE AND RADIO ELECTRONICS»

ABSTRACT

On the topic of:

"TECHNOLOGICAL PROCESS OF PROCESSING

OPTICAL PARTS (general basics)"

MINSK, 2008

Basic technological operations

The technological process of manufacturing optical parts consists in processing their working and mounting surfaces. The blanks (lump glass, tiles, pressing, etc.) are given the required dimensions, and the surfaces are structured in accordance with their purpose.

Auxiliary operations (sticker, gluing, blocking, etc.) are used to attach parts to fixtures and group them for joint further processing or to remove all kinds of contaminants (washing, wiping).

As a polishing tool, faceplates, mushrooms and cups are used, on which a layer of resin or fibrous materials is applied.

Fig.1. Scheme of formation of decentering:

and the skew of the axis of the column of blanks; b displacement of the center of the spherical surface

Rice. 2. Decentering in the lens:

and the optical axis is parallel to the geometric axis; b optical axis at an angle to the geometric axis

Rice. 3 Schematic representation

Fig.4. Automatic lens mounting by compression between cartridges:

1 lens; 2 cartridges

The installation of the lens on the cartridge before centering is carried out optically or mechanically.

Optical method installation by "glare" on the eye or under the optical tube. The lens is fixed with a centering resin on a rotating cartridge in a position in which the immobility of the image of the lamp filament or the image of the "glare" in the optical tube is ensured.

The mechanical method (self-centering) consists in the fact that the lens is installed automatically by compression between two cartridges located strictly on the same axis (Fig. 4).

With both methods, the correct installation is guaranteed by good preparation and trimming of the mounting edge of the cartridges and the absence of runout of the centered part during rotation.

Gluing. The task of gluing is to obtain a rigidly fastened and centered system.

In some cases (especially for flat parts), gluing is replaced by optical contact (molecular adhesion of two polished surfaces).

Auxiliary technological operations

The most important auxiliary operation is blocking the connection of parts or workpieces with a device (sticker, mechanically, by optical contact, vacuum fastening, fitting into separators, etc.) for their joint further processing. The combination of a fixture and parts or blanks fixed to it is called a block. The quality of the product and the efficiency of the technological process depend to a large extent on the correct choice of the method of blocking, depending on the size and shape of the parts, the given accuracy.

Blocking should provide:

1) fixing the maximum number of blanks;

2) ease of processing in this operation (for example: grinding, polishing);

3) convenience to make the necessary measurements in the process of work;

4) reliability of fastening at the most intensive mode of operation;

5) the absence of mechanical damage and deformation of blanks or parts;

6) the correct and symmetrical arrangement of the processed surfaces relative to the fixture and the processing tool;

7) ease and speed of locking and unlocking.

In optical production, several methods of blocking are used. However, the most common so far is the method of elastic fastening.

Elastic mount. It is used in small-scale and mass production for medium-precision parts. This operation includes the following transitions:

1. Sticker on one of the machined sides of the resin cushion part by hand